Lubricating oil



Patented .lune 18, 1940 PATENT OFFICE 2,204,680 LUBRICATING on.

Robert Charles Cantelo, Hammond, Ind., assignor to Sinclair Refining Company, New York, N. Y., a corporation oi Maine No Drawing.

5 Claims.

This invention relates to the compounding of petroleum oils and, moreparticularly, to them- 'orporation in petroleum lubricating oils of an ddition agent having the effect of improving the physical characteristics and lubricating properties of the oils. The invention includes a novel addition agent having the effect of improving the physical characteristics and lubricating properties of petroleum hydrocarbon oils and also inh eludes an improved compounded petroleum hydrocarbon oil containing the novel addition agent of the invention. I l

Of the numerous prerequisites for a petroleum lubricating oil satisfactory for use in internal ll combustion engines, three are of major importance. The oil must be stable during storage, handling and use so that deterioration of the physical properties of the 01], particularly during use, will not occur. Secondly the oil should be substantially non-corrosive toward the bearings used in internal combustion engines so that the wear and loss of weight, of these bearings is reduced to a minimum. Furthermore, the oil must have a film strength of sufficient magnitude to insure efilcient lubrication of internal combustion engines and to eliminate the possibility of scoring of moving parts caused by the breakdown of the lubricating film between these moving parts.

Petroleum lubricating oils frequently have a tendency to deteriorate merely as a matter of time and such tendency is much more common under conditions of use, particularly where the oil is maintained at an elevated temperature for prolonged periods. Such deterioration becomes pronounced .and results in serious changes in the composition and characteristics of the oil when the oil is used for lubricating internal combustion engines such as are employed in modern automobiles and aeroplanes where the oil, is in contact with rapidly moving and highly heated engine parts. Such deterioration of lubricating oil is characterized, in one aspect, by the formation of heavy sludge which tends to collect in the oil a pump and oil lines of the engine and eventually to clog them to such an extent as to prevent or greatly impair the efllcient lubrication of the engineQ This deterioration further causesan increase in the viscosity of thelubricating oil there- 0, by subjecting the engine to a correspondingly increased load.

The corrosive characteristics of these lubricating oils are of particular importance in view of the present trend toward the substitution of beara ing metals such as cadmium-silver and copper- Application January 24, 1938, Serial No. 186,581

bronze alloys for the previously used Babbitt metal. Babbitt bearings are generally highly resistant to corrosion; the new types of bearing alloys are more susceptible to corrosion, Any corrosive action of lubricating oils increases markedly with increasing temperatures and, consequently, presents a very serious problem where, as in modem internal combustion engines, the lubricating oil temperatures frequently are as high as 200 to 350 F. during normal operation. The seriousness m of the problem can be illustrated by example:

A highly refined Pennsylvania motor oil which, at

an operating temperature of 350 F. efl'ected a loss by corrosion of only 0.4 milligram of a Babbitt bearing in 24 hours, under similar operating con- 1 ditions efiected a loss of 2012 milligrams of a cadmium-silver bearing substituted for that Babbitt bearing in the same The film strength of these lubricating oils is of particular importance in view of the high pressures encountered between moving parts of the modern internal combustion engines. A high film strength insures the complete protection of moving parts by insuring the presence of a film of the lubricating oil between these moving parts. 25 A breakdown of such a film due to inferior film strength results in the scoring and undue wear of adjacent moving parts.

Special methods have been devised for measuring the above-mentioned prerequisites of lubriso eating oils under various conditions.

A generally satisfactory method of measuring the stability of lubricating oils in terms of the rate of sludge-formation'has been described in the Society of Automotive Engineers Journal, Vol. 34, No. 5, page 1'72. According to this method the time is determined in which 10 milligrams of sludge are formed in 10 grams of the oil maintained at a definite temperature while air is bubbled through the oil at a specified rate. This time, expressed in hours, is designated sludging time? and is a measure of the rate of sludgeformation in that particular" oil under the particular conditions of the test. The term sludging time as used hereinafter refers to the abovedetermined measure of the rate of sludge formation and is a relative measure of the stability of lubricating oils under conditions of storage or use. 1

A generally satisfactory method for determinso 1 ing the corrosive action of lubricating oils may be carried out with the Sinclair bearing corrosion test machine. In determining the corrosive properties of lubricating oils referred to herein I have used this test'machine. This test machine com- '5 prises a test chamber the cover portion of which comprises a lead alloy bath which may be heated,

by electrical resistance units. A shaft extends through the interior of the test chamber, and this Shaft has four cross arms mounted at 90 to one another at spaced intervals along the shaft. The shaft is so positioned within the test chamber that when the chamber is partially filled .with a lubricating oil to be tested the cross arms dip into the oil as the shaft is rotated. The hearings to be tested are attached to a removable bar positioned within the test chamber onone side wall thereof above the level of oil within the chamber, and each test bearing is attached to the removable bar at a point opposite each set of cross arms mounted on the shaft. As the shaft .is rotated a stream of the test oil is directed by each of the cross arms against, each of the test The test oil is maintained at 350 F., the lead alloy bath is maintained at a temperature of 500 F., and air is passed through the test chamber-at a rate of one cubic foot per minute. The second stage of the test is conducted for 20 hours using another set of weighed bearings. The test oil is maintained at 280 F., the lead alloy bath is maintained at a temperature of 430 F., and air is passed through the test chamber at a rate of one cubic foot per minute. Each set of bearings is removed after each stage of the test, these bearings are weighed, and the loss in weightof each bearing in each stage is reported in milligrams. A loss of bearing metal through corrosion as determined by the above test substantially in excess of 100 milligrams in either stage of the test indicates that the particular lubricating oil is excessively corrosive with respect to bearings of the type tested. Though it is desirable to reduce the corrosive action of the oil to a minimum it is usually sufficient for practical purposes that such action be so reduced as to effect a loss of not substantially greater than .100 milligrams in either stage of the test.

A representative comparison of the film strength of different samples of lubricating oil may be obtained by the use of the Faville-LeVally test machine. This test machine measures the point, expressed in pounds pressure applied in the machine, at which a fllm of lubricating oil breaks down between two metal parts, one part moving with respect to the other. Although this machine does not necessarily determine the actual film strength of a particular sample of lubricating oil, it has been found to offer a useful v means of comparing the relative film strength of different samples of lubricating oils.

I have discovered that-the physical characteristics and lubricating properties of petroleum lubricating oils may be greatly improved by incorporating in such oils a small proportion of thiobenzophenone [(CsH5)zC=S]. The incorporation in a lubricating oil of a small proportion of thiobenzophenone, hereinafter referred to as the addition agent, improves 'the stability of the oil as shown by an increase in the sludging time, decreases the corrosive effect of the oil on internal combustion engine bearings and the like, and also increases the film strength of the oil as indicated by an increase in the breakdown point of the oil. I have found that, in general, these improvements in'the physical characteristics and lubricating properties of the oil are realized by the incorporation in the oils of between 0.1% and 3.0% of the addition agent by weight on the oil. I a

The thiobenzophenone used in accordance with my invention may be prepared, for example, by first producing benzophenone dichloride :from benzophenone, and subsequently reacting the benzophenone dichloride with sodium hydrosulphide.-

In preparing the thiobenzophenone referred to further herein in examples of my invention, 364

parts (by weight) of benzophenone and 412 parts of phosphorous penta chloride were heated at 302 F. for a period of .two hours. The phosphorous oxychloride thus formed was removed from the mixture by distillation. The residue from this distillation was then distilled under a sub-atmospheric absolute pressure of millimeters. The fraction boiling between 394 398 F. was collected, this fraction comprising 284 parts of benzophenone dichloride. The benzophenone dichloride was placed in a reaction vessel equipped with a stirring device and means for providing an inert atmosphere within the reaction vessel. An alcoholic solution of sodium hydrosulphide was then prepared by dissolving 100 parts of metallic sodium in about 790 parts of absolute alcohol and saturating this solution with hydrogen sulphide gas. This solution was then addedslowly to the benzophenone dichloride while stirring the reaction mixture vigorously and while passingcarbon dioxide through the reaction vessel to maintain aninert atmosphere. The temperature of the reaction mass was held below 50 F. by means of an ice bath surrounding the reaction vessel. After all of the sodium hydrosulphide solution had been added, the mixture was allowed to stand for a period of about two hours at the end of which period about 1000 parts of water were added. The thiobenzophe none was extracted from this mixture by means of ether whereupon the ether solution was dried over anhydrous calcium chloride, the solution decanted, and the ether removed from the extract by distillation. The residue of this distillation was distilled at a subatmosphe'ric absolute pressure of 14millimeters in an atmosphere of carbon dioxide, and the fraction boiling, at 345-346 F. was collected. This fraction comprises the thiobenzophenone which I use in the practice of my invention. Upon cooling, the above-mentioned portion was obtained as a blue oil containing blue needle-like crystals. An analysis of the sulphur content of this fraction indicated that the compound contained about 12% sulphur. Inasmuch as thiobenzophenone theoretically contains 16.2% sulphur, it appears that the product which I use in accordance with my invention and which is referred to herein as thiobenzophenone comprises about 75% thiobenzophenone and the remainder unconverted benzophenone. This mixture can not easily be separated by further fractional distillation. It should be noted, however, that substantially pure thiobenzophenone alone may be used with advantage or this pure compound may be blended with benzophenone to produce a satisfactory addition agent. I have found, however, that the mixture of thiobenzophenone and benzophenone prepared as described above be used with particular advantage in the practice of my invention.

A more complete understanding of my invention may be had upon consideration of the following examples which have been reproduced in tabular form. It must be understood that these examples should in no way be construed as a limitation of the scope of my] invention 'inasmuch as these examples are given merely to illustrate the improved results obtained by incorporating in lubricating oils a small proportion of thiobenzophenone.

Table I shows the effect of varying percentages of the addition agent of my invention in a Pennsylvania motor oil. This oil, before the incorporation therein of the addition agent, had a gravity of 28.6 A. P. I., a viscosity of 445 seconds Saybolt Universal at 100 F., a viscosity of 61.9 seconds Saybolt Universal at 210 F., a viscosity index of 103.6 and a pour point of 5 F. The stability of the. uncompounded oil and of the blended oil is indicated by the sludging time thereof. Thereis listed in Table I the length of time required to form 10 milligrams of sludge (tar) per 10grams of oil sample as well as thelength of time required toproduce 100 milligrams of sludge per 10 grams of oil sample. These results are designated the sludging time for the formation of 0.1% tar" and 1.0% tar," respectively.

Table 1 Percent addition agent 0. 1.0 2.0 3.0

Sludging time (0.1% tar) 76 100 98 100 102 Bludging time (1.0% tar) 97 114 116 110 120 particular oil. It will be seen, therefore, that beneficial results may be obtained over a wide range of proportions of the addition agent in this lubricating oil.

Table II shows the effect of varying proportions of the addition agent on the corrosive action of the Pennsylvania motor oil referred to in Table I when used to lubricate cadmium-silver bearings. The results obtained with varying proportions of the addition agent are shown for both stages of the bearing-corrosion test, and the corrosiveness of the different samples is indicated by the loss of weight in milligrams of the hearing metal during each stage of the test.

, Table II Peroentaddition agent .Q. oas roao 3.0

First stage, loss, mgr 1457 02 28 0.0 6 Second stage, loss, mgr 1290 38 10 7 27 The corrosive action of this lubricating oil with respect to copper-lead bearings is not as marked-. ly reduced by the incorporating in the oil of a small proportion of the addition agent as in the case of cadmium-silver bearings, although the compounded oil may be used with particular advantage in the lubrication of copper-lead bearngs.

Table III' shows the effect of varying proportions of the addition agent upon-the film strength of the Pennsylvania motor oil referred to in connection with Tables I and II. The film strength of this lubricating oil is indicated by the breakdown point of the oil sample, measured in pounds, as determined by the Faville-LeVally test machine.

An amount of the thiobenzophenone up to at least 3.0% by weight is shown in Table III to be highly effective in increasing the film strength of this particular motor lubricating oil. It should be noted, however, that as little as 0.5% by weight of the addition agent markedly increases the film strength of this oil. A smaller proportion of the addition agent may also be used with advantage.

It will be seen from the foregoing examples that salientimprovements may be made in the physical characteristics and lubricating proper ties of petroleum lubricating oils by the incorporation therein of a. small proportion of thiobenzophenone. The stability of the oils may thus be increased, the corrosive nature of the oils diminished, and the film strength of these lubricants markedly improved. Although the thiobenzophenone has been illustrated herein with respect to its effect on a particular Pennsylvania motor oil, it should be noted that this addition agent may be used with advantage with other lubricating oils where it is desired to increase the stability, decrease the corrosive nature, or increase the film strength of these other oils, or effect a combination of these results. Thus, for example, when the addition agent of my invention is incorporated in a substantially non-corrosive lubricating oil the stability and film strength of the oil will be improved although no noticeable improvement may be observed in the corrosive nature of the oil.

Moreover, a larger or smaller proportionof the addition agent than the proportions noted in the foregoing illustrations may be used advantageously with other oils. As little as 0.1% by weight of the addition agent may be sufflcient in many instances to produce the desired efiect. The optimum proportion of the addition agent which may be used in each particular. instance may be readily ascertained by the simple tests hereinbefore described, this optimum proportion depending not only upon the characteristics of the oils but also upon the property or properties of the oil which it is desired to improve.

Although the use of the addition agent of my l0 of the addition agent 01' my invention may reduce or enhance the effect of the other addition: agents in the compounded oils. Thus, by the incorporation of a small proportion of the addition agent of my invention in a compound lubrieating oil containing certain wax acid esters having the property of increasing the viscosity index of the oil, this increase in the viscosity index of the'oil is maintained and the stability of the oil is markedly'improved. On the other hand, the incorporation of a small proportion the corrosive effect of another addition agent incorporated in a blended lubricating oil for the purpose of improving some physical characteristic of the oil.

1. An improved lubricating oil which comprises a petroleum lubricating oil containing a small proportion of thiobenzophenone.

2. An improved lubricating oil which comprises a petroleum lubricating oil containing between about 0.1% and 3.0% by weight 01' thiobenzophenone.

3. An improved lubricating oil which comprises a petroleum lubricating oil containing between about 0.5% and 1.0% by weight of thiobenzophenone.

4. An improved lubricating oil which comprises a petroleum lubricating oil containing a small proportion of a mixture of thiobenzophenone and benzophenone.

5. An improved lubricating oil which comprises i a petroleum lubricating oil containing between about 0.1% and 3.0% by weight of a mixture of about 75% thiobenzophenone and about 25% benzophenone. I

ROBERT CHARLES CANTELO. 

